JS复制文本到剪切板

function copyToClipboard(txt) {  
     if(window.clipboardData) {  
       window.clipboardData.clearData();  
       window.clipboardData.setData("Text", txt);  
       alert("Your request has been processed successfully.");  
     } else if(navigator.userAgent.indexOf("Opera") != -1) {  
      window.location = txt;  
     } else if (window.netscape) {  
      try {  
       netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");  
      } catch (e) {  
       alert("被浏览器拒绝！\n请在浏览器地址栏输入'about:config'并回车\n然后将'signed.applets.codebase_principal_support'设置为'true'");  
      }  
      var clip = Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);  
      if (!clip)  
       return;  
      var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);  
      if (!trans)  
       return;  
      trans.addDataFlavor('text/unicode');  
      var str = new Object();  
      var len = new Object();  
      var str = Components.classes["@mozilla.org/supports-string;1"].createInstance(Components.interfaces.nsISupportsString);  
      var copytext = txt;  
      str.data = copytext;  
      trans.setTransferData("text/unicode",str,copytext.length*2);  
      var clipid = Components.interfaces.nsIClipboard;  
      if (!clip)  
       return false;  
      clip.setData(trans,null,clipid.kGlobalClipboard);  
      alert("Your request has been processed successfully.");  
     }  
    }